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calculus of variations

...are called variational principles and are usually expressed by stating that some given integral is a maximum or a minimum. One example is the French mathematician Pierre-Louis Moreau de Maupertuis’s
principle of least action (
c. 1744), which sought to explain all processes as driven by a demand that some property be economized or minimized. In particular, minimizing an integral, called an...

extremal principle

...These arise in many problems where the unknown is itself a function of some variable, and especially in those parts of physics that are expressed in terms of extremal principles (such as the
principle of least action). The extremal principle usually yields information about an integral involving the sought-for function, hence the name
integral equation. Hilbert’s contribution was...

A similar extremal principle in mechanics, the
principle of least action, was proposed by the French mathematician and astronomer Pierre-Louis Moreau de Maupertuis but rigorously stated only much later, especially by the Irish mathematician and scientist William Rowan Hamilton in 1835. Though very general, it is well enough illustrated by a simple example, the path taken by a particle between...

work of

Feynman

...in molecules. Feynman received his doctorate at Princeton University in 1942. At Princeton, with his adviser, John Archibald Wheeler, he developed an approach to quantum mechanics governed by the
principle of least action. This approach replaced the wave-oriented electromagnetic picture developed by James Clerk Maxwell with one based entirely on particle interactions mapped in space and time....

Maupertuis

In 1744 Maupertuis enunciated the
principle of least action, later published in his
Essai de cosmologie (1750; “Essay on Cosmology”). It states simply that “in all the changes that take place in the universe, the sum of the products of each body multiplied by the distance it moves and by the speed with which it moves is the least [that is] possible.” The German...